The present invention relates to an evaporator with a cool storage function for use in a car air conditioner for a vehicle in which an engine serving as a drive source for a compressor is temporarily stopped when the vehicle is stopped.
In the present specification and appended claims, the upper, lower, left-hand, and right-hand sides of FIGS. 1, 3, and 8 will be referred to as “upper,” “lower,” “left, and “right,” respectively.
In recent years, in order to protect the environment and improve fuel consumption of automobiles, there has been proposed an automobile designed to automatically stop the engine when the automobile stops, for example, so as to wait for a traffic light to change.
However, an ordinary car air conditioner has a problem in that, when an engine of an automobile in which the air conditioner is mounted is stopped, a compressor driven by the engine is stopped, and supply of refrigerant to an evaporator stops, whereby the cooling capacity of the air conditioner sharply drops.
As one measure to solve such a problem, imparting a cool storage function to the evaporator has been considered, to thereby enable cooling of a vehicle compartment by releasing the cool stored in the evaporator, when the compressor stops as a result of stoppage of the engine.
An evaporator with a cool storage function has been proposed (see Japanese Patent Application Laid-Open (kokai) No. 2011-12947). In the proposed evaporator, a plurality of flat refrigerant flow tubes which extend in the vertical direction and whose width direction coincides with an air-passing direction are disposed in parallel such that they are spaced from one another. The evaporator has air-passing clearances each formed between refrigerant flow tubes located adjacent to each other. Cool storage material containers filled with a cool storage material are disposed in some air-passing clearances, and outer fins are disposed in the remaining air-passing clearances. The outer fins are disposed in the air-passing clearances adjacently located on opposite sides of each air-passing clearance in which the corresponding cool storage material container is disposed. Each cool storage material container includes an inner fin disposed therein. A plurality of convex portions which bulge outward are formed on each of the left and right side walls of the cool storage material container such that each side wall is studded with the convex portions. The bulging top walls of the convex portions are in contact with the corresponding refrigerant flow tube. The convex portions of one side wall of each cool storage material container are identical in shape and size with the convex portions of the other side wall of the cool storage material container, and are provided at the same locations as those of the convex portions of the other side wall as viewed from the left side or the right side. The inner fin is joined to portions of the left and right side walls of the cool storage material container where the convex portions are not formed. As viewed from the left side or the right side, the portions of the left and right side walls of the cool storage material container where the convex portions are not formed are contact portions which are in contact with the inner fin, and the portions of the left and right side walls which correspond to the bulging top walls of the convex portions are noncontact portions which are not in contact with the inner fin.
The evaporator with a cool storage function disclosed in the publication operates as follows. In an ordinary cooling period in which a compressor is operating, the cool carried by the refrigerant flowing through the refrigerant flow tubes is transferred directly to the cool storage material within each cool storage material container from the bulging top walls of the convex portions of the two side walls of the cool storage material container, the bulging top walls being the noncontact portions of the two side walls which are not in contact with the inner fin and which are in contact with the corresponding refrigerant flow tubes. Also, the cool carried by the refrigerant is transferred from the contact portions of the two side walls, which are in contact with the inner fin, to the cool storage material in the cool storage material container via the inner fin. Thus, the cool is stored in the cool storage material. Meanwhile, when the compressor stops, the cool stored in the cool storage material within each cool storage material container is transferred directly to the two side walls of the cool storage material container, or is transmitted from the inner fin to the two side walls of the cool storage material container through the contact portions which are in contact with the inner fin. Subsequently, the cool is transferred to the corresponding refrigerant flow tubes through the bulging top walls of the convex portions. The cool is then transferred through the refrigerant flow tubes to the outer fins disposed in the air-passing clearances adjacently located on the opposite sides of the air-passing clearance in which the cool storage material container is disposed. Subsequently, the cool is released from the outer fins to air flowing through the air-passing clearances.
However, the evaporator with a cool storage function disclosed in the publication has the following problem. In the disclosed evaporator, the convex portions of one side wall of each cool storage material container are identical in shape and size with the convex portions of the other side wall of the cool storage material container, and are provided at the same locations as those of the convex portions of the other side wall as viewed from the left side or the right side. The portions of the left and right side walls of the cool storage material container where the convex portions are not formed are contact portions which are in contact with the inner fin, and the bulging top walls of the convex portions are noncontact portions which are not in contact with the inner fin. Therefore, in an overlap region where the left and right side walls of each cool storage material container overlap with the corresponding refrigerant flow tubes as viewed from the left side or right side of the cool storage material container, the total area of the contact portions of each of the left and right side walls of each cool storage material container which are in contact with the inner fin is smaller than the total area of the noncontact portions thereof which are not in contact with the inner fin. Accordingly, in both the period during which cool is stored and the period during which cool is released, the efficiency of heat transfer between the left and right side walls of each cool storage material container and the cool storage material stored therein, which transfer is performed through utilization of the inner fin is not sufficiently high. Therefore, the conventional evaporator is unsatisfactory in terms of cool storage performance and cool release performance.